The present invention relates to a plate-type heat exchanger and a joint structure thereof, in which an aluminum group material is used and a junction is made by use of a plate material with its opposite surfaces clad with an aluminum material, and for use in a cooler/heater heat pump, an oil cooler, etc.
FIG. 7 shows a conventional plate-type heat exchanger, for example, as disclosed in Japanese Utility Model Publication No. Sho-50-27020, and FIG. 8 is a partial section of FIG. 7. In the drawings, the reference numeral 1 designates a plate; 2, a groove to which a packing is to be applied; 3, a first fluid inlet; 4, a first fluid outlet; 5, a second fluid inlet; and 6, a second fluid outlet. In FIG. 8, the reference numeral 7 designates a packing. The plates 1 in each of which the packing 7 is put in the groove 2 are stacked on one another and fixed by bolts and nuts (not shown) so as to form each tightly closed first and second fluid passages. "A" designates a first fluid and "B" designates a second fluid. Thus, the plates 1 having their grooves 2 with the packings 7 are laminated successively one on one so the first and second fluid communication passages are formed alternately.
Next, a prior art relating to a joint structure of such a plate-type heat exchanger will be described. FIG. 9 is a perspective view showing the state of constituent parts, before joining, of a conventional plate-type heat exchanger (heat sink), for example, as disclosed in Japanese Patent Application No. Hei-1-124154, and FIG. 10 is a perspective view showing the state in which the junction of the plate-type heat exchanger of FIG. 9 has been completed. In the drawings, the reference numeral 31 designates an upper plate having holes 31a and 31b to which inlet and outlet pipes for a heat exchange fluid such as a refrigerant, that is, a cooling fluid; 32, a lower plate; 33, an intermediate plate made of a brazing sheet having a passage 33a through which the cooling fluid flows and having opposite surfaces clad with a brazing material; 34, an inlet pipe which is made of an aluminum material and through which the cooling fluid flows in; and 35, an outlet pipe which is made of an aluminum material and through which the cooling water flows out. These parts are assembled as shown in FIG. 10 and a brazing material for aluminum is set to the inlet pipe 34 and the outlet pipe 35 so that the whole of the plate-type heat exchanger is brazed at aluminum brazing temperature.
Next, operation will be described. First, with respect to FIG. 7, the first fluid A flows from the first fluid inlet 3 to the first fluid outlet 4, and the second fluid B flows from the second fluid inlet 5 to the second fluid outlet 6. The first and second fluids A and B flow, in opposition to each other, respectively through the first and second fluid communication passages tightly sealed by the plates 1 and the grooves 2 with packings 7, and perform heat exchange therebetween through the plates 1.
Next, the operation of FIG. 9 and the method of producing the joint portion will be described. In the conventional plate- type heat exchanger, an a apparatus such as an electronic apparatus (not shown) which may generate heat is fixed on the lower plate 32 in a contacting relation, and an aluminum pipe is connected to the inlet pipe 34 through torch brazing (not shown), so that a cooling fluid is made to flow in through the inlet pipe 34. The cooling fluid flows to the outlet pipe 35 and performs heat exchange between the cooling fluid and the apparatus which may generate heat through the lower plate 32 to thereby cool the apparatus. The cooling fluid which has been warmed through the heat exchange flows out from the outlet pipe 35. The cooling fluid passes through an aluminum pipe connected to the outlet pipe 35 similarly to the inlet pipe 34, then cooled in the outside of the heat exchanger, and then flows into the inlet pipe 34 again.
Having such a configuration, the conventional plate-type is not stable in the state of air tightness and has a possibility that may occur or substance to be treated may be polluted in accordance with the quality of the packings. The conventional heat exchanger has further problems in that the cost of formation of metal molds for plates is high, design change cannot be made easily, etc.
Further, such a conventional plate-type heat exchanger producing method in which air tightness is provided by brazing joining as described above has problems in that it is necessary to join the aluminum pipes with the fluid outlet and inlet 34 and 35 by brazing or welding after assembling with aluminum brazing so that the brazed portion of the plate-type heat exchanger may be damaged or the joining work at the joint portions between the aluminum pipes and the fluid outlet and inlet portions is troublesome because of a narrow space at the joint portions to thereby make it possible to easily generate defective portions at the joint portions.
In the case where a heat exchanger (not shown) connected to the outside of the plate-type heat exchanger has a copper piping 39, the joining between an aluminum pipe and a copper pipe is difficult, and conventionally, as shown in FIG. 11, therefore, an AC joint 38 composed of a copper pipe 36 and an aluminum pipe 37 which are joined with each other through projection welding is brazed at its aluminum side 37 to the plate type heat exchanger, and the copper pipe 39 is joined to the AC joint 38 at the copper side 36 thereof. Accordingly, in addition to the above-mentioned problems, there has been a problem that copper and aluminum are in direct contact with each other to thereby generate electrolytic corrosion because of a large electric potential between the copper and aluminum.